<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
</head>
<body>
	<!-- <div style="display:block;position:relative;">
		<div style="position:absolute;top:50%">
			<div style="position:relative;top:-50%">
				<div style="background-color:red;width:400px;height:300px;">
			
				</div>
			</div>
		</div>
	</div> -->
	<div style="width: 800px; height: 400px; display: block; position: relative; background-color: green;overflow:hidden;">
		<div style="left: 50%; top: 50%; position: absolute;">
			<div style="left: -50%; top: -50%; position: relative;">
				<div style="width: 400px; height: 300px; background-color: red;">
			
				</div>
			</div>
		</div>
	</div>
</body>
</html>